How to replace a word inside a string in PHP

Use the PHP str_replace() function

You can use the PHP str_replace() function to replace all the occurrences of a word within a string.

In the following example the word "facts" is replaced by the word "truth".

<?php
$my_str = 'If the facts do not fit the theory, change the facts.';
 
// Display replaced string
echo str_replace("facts", "truth", $my_str);
?>

The PHP str_replace() function is case-sensitive, however if you want to perform case-insensitive match and replace you can use the str_ireplace() function.